(a) Field of the Invention
The present invention relates to a radio frequency identification tag and a radio frequency identification tag antenna. Particularly, it relates to a radio frequency identification tag and a radio frequency identification tag antenna using a stacked structure.
The present invention was supported by the IT R&D program of MIC/IITA [2006-S-023-02, Development of Advanced RFID System Technology].
(b) Description of the Related Art
A radio frequency identification (RFID) tag is used in various fields such as distribution and material handling industries, together with an RFID reader. In general, an RFID system includes an RFID tag and an RFID reader.
When an object to which the RFID tag is attached accesses a read zone of the RFID reader, the RFID reader transmits an interrogation signal to the RFID tag by modulating a continuous electromagnetic wave having a specific frequency. Then, the RFID tag transmits back the electromagnetic wave transmitted from the RFID reader after performing back-scattering modulation in order to transmit information stored in the RFID tag's internal memory. The back-scattering modulation is a method for transmitting tag information by modulating the amplitude and/or the phase of a scattered electromagnetic wave when the RFID tag transmits the electromagnetic wave that is initially transmitted from the RFID reader back to the RFID reader by scattering the electromagnetic wave.
A passive RFID tag rectifies the electromagnetic wave transmitted from the RFID reader and uses the rectified electromagnetic wave as its own power source to acquire operation power, and the intensity of the electromagnetic wave transmitted from the RFID reader should be larger than a specific threshold value for normal operation of the passive RFID tag.
Since the intensity of the signal is decreased when a distance between the RFID reader and the RFID tag is increased, the transmission power of the RFID reader should be increased so as to increase a range within which the RFID reader can read the RFID tag in the RFID system. Hereinafter, the range between the RFID reader and the RFID tag is referred to as a readable range. However, it is not possible to unconditionally raise the level of the transmission power because the transmission power of the RFID reader is limited by local regulations of each country, and therefore, the RFID tag should efficiently receive the electromagnetic wave transmitted from the RFID reader so as to maximize the readable range with the limited transmission power.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.